What is the difference between living longer and living longer in good health?
Healthspan and lifespan are two separate things: you can live a long time yet lose years to illness and decline. Calorie restriction and fasting have the strongest support for improving both; for supplements such as NMN, the evidence in people is still too limited for firm recommendations.
Lifespan is the total number of years you live; healthspan is the portion of those years in which you are healthy and functioning well. The two diverge in measurable ways. Research into biological ageing shows that someone who is 50 by the calendar can already be biologically closer to 65, with a correspondingly higher risk of early death, cancer, reduced physical functioning, and Alzheimer's disease. The reverse is also possible: a person can be biologically younger than their passport age. Living longer without adding healthy years is explicitly not the goal of modern ageing research.
Why does healthspan run out before lifespan does? Two processes play a central role. First, cells that have aged and stopped dividing build up in tissues. They do not die off, but they continuously release substances that irritate and damage surrounding tissue and drive disease. Second, the internal waste-disposal system inside cells, which breaks down and recycles damaged material, grows weaker over time. When that system performs less well, damaged proteins and cell components accumulate. Both processes erode quality of life long before they become fatal.
What can you do about it? Calorie restriction with adequate nutrition is the best-supported approach: in rodents and primates it extends both healthy years and total lifespan, partly by activating the waste-disposal processes mentioned above. Intermittent fasting has similar effects by the same mechanisms and appears safe, although the evidence in people for extending lifespan is not yet conclusive. The gut microbiome also plays a role: in mice that aged prematurely, a transplant of healthy gut bacteria improved health and lifespan, but this has not yet been translated to healthy people.
NMN supplements (a building block for NAD+, a substance cells need for energy and repair) are popular, but the evidence is preliminary. In a small study of 80 middle-aged adults over 60 days, NAD+ levels rose at all doses, walking distance improved, and participants reported better health. The study was short, the group was small, and one author worked for the manufacturer. That last point does not automatically make the findings wrong, but it calls for caution until larger independent studies confirm them. Senolytics, compounds that clear out worn-out cells, look promising in animal studies, but evidence in people is still almost entirely lacking.
Claims are based on nine sources. The mechanistic and animal-study evidence is consistent; evidence from human intervention studies is limited to a small number of small studies and people followed over time.
How big is the difference between your biological and calendar age?
The typical spread between your biological and calendar age is around one to two years. Studies name no firm upper limit, but biological age does predict health risks better than your birth year.
Does your body age faster after a prolonged period of stress?
Prolonged stress is associated with signs of faster cellular ageing, but whether this is truly causal and applies to everyone has not yet been proven. If you want to limit the biological consequences of stress, it pays to pay attention to how you personally experience and process stressful situations.
Does your telomere length tell you anything useful about your health?
Telomere length is a relevant biological measure, but does not give a clear-cut signal: shorter telomeres increase the risk of heart disease and fibrosis, while longer telomeres increase the risk of certain cancers. A commercial telomere test in blood is therefore difficult to translate into concrete health advice.
Is it true that women age more slowly biologically than men?
Multiple studies confirm that women are biologically younger than men of the same age, but women also spend their extra years more often in poorer health. The difference is therefore real, but more complex than the simple conclusion that 'women age more slowly'.
Can you lengthen your telomeres through lifestyle?
Lifestyle can probably slow telomere shortening, but the starting length of your telomeres is largely genetically determined and by far the strongest predictor of how quickly they shorten. Not smoking, exercising regularly and following a Mediterranean diet are the most well-supported steps you can take.
Which lifestyle factors influence your biological age the most?
Sitting for prolonged periods, a disrupted circadian rhythm and muscle loss are the best-supported negative factors for your biological age; exercising regularly and maintaining a consistent sleep-wake rhythm are the most concrete steps you can take right now.